Methods and apparatuses for removing material from discrete areas on a semiconductor wafer

ABSTRACT

Methods and apparatuses for removing material from discrete areas on a semiconductor wafer are described. In one implementation, an etchant applicator is provided having a tip portion. Liquid etchant material is suspended proximate the tip portion and the etchant applicator is moved, together with the suspended liquid, sufficiently close to a discrete area on a wafer to transfer liquid etchant onto the discrete area. In various embodiments the tip portion can comprise fluid permeable materials, fluid-absorbent materials, and/or wick assemblies. An exhaust outlet can be provided operably proximate the tip portion for removing material from over the wafer. The tip portion can be moved to touch the discrete area.

TECHNICAL FIELD

This invention relates to methods and apparatuses for removing materialfrom discrete areas on a semiconductor wafer, and in particular tomethods and apparatuses for removing material from over alignment markson a wafer.

BACKGROUND OF THE INVENTION

It is sometimes desirable in semiconductor device manufacturing toremove material from over discrete wafer areas, without exposing otherwafer areas to the etchant solutions. One type of discrete area includesalignment marks which are used to align wafers during processing.Alignment marks are preferably kept substantially clear of contaminantsor material so that processing equipment can easily locate them.Alignment marks can get covered with a variety of material includingphotoresist, etched substrate material, and chemical mechanicalpolishing slurry or a variety of thin films. When alignment marks getcovered with material, it is desirable to remove the material. Methodsand apparatuses for removing material from over alignment marks aredescribed in U.S. Pat. No. 5,271,798, which is assigned to the assigneeof this document, the disclosure of which is incorporated by reference.

This invention arose out of concerns associated with providing improvedmethods and apparatuses for removing material from discrete areas, e.g.alignment marks, on a semiconductor wafer.

SUMMARY OF THE INVENTION

Methods and apparatuses for removing material from discrete areas on asemiconductor wafer are described. In one implementation, an etchantapplicator is provided having a tip portion. Liquid etchant material issuspended proximate the tip portion and the etchant applicator is moved,together with the suspended liquid, sufficiently close to a discretearea on a wafer to transfer liquid etchant onto the discrete area. Invarious embodiments the tip portion can comprise fluid permeablematerials, fluid-absorbent materials, and/or wick assemblies. An exhaustinlet can be provided operably proximate the tip portion for removingmaterial from over the wafer. The tip portion can be moved to touch thediscrete area.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a top plan view of a semiconductor wafer showing an exemplarydiscrete area.

FIG. 2 is a diagrammatic side sectional view of an exemplary discretearea comprising alignment marks.

FIG. 3 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 2.

FIG. 4 is a side elevational view of an etchant applicator constructedin accordance with one embodiment of the present invention.

FIG. 5 is a view of a tip portion of the FIG. 4 applicator in accordancewith one embodiment of the invention.

FIG. 6 is a view of a tip portion of the FIG. 4 applicator in accordancewith another embodiment of the invention.

FIG. 7 is a view of a tip portion of the FIG. 4 applicator in accordancewith another embodiment of the invention.

FIG. 8 is a view of a tip portion of the FIG. 4 applicator in accordancewith another embodiment of the invention.

FIG. 9 is a view of a tip portion of the FIG. 4 applicator, undergoingprocessing in accordance with one or more embodiments of the presentinvention.

FIG. 10 is a view of a tip portion of the FIG. 4 applicator, undergoingprocessing in accordance with one embodiment of the present invention.

FIG. 11 is a view of a tip portion of the FIG. 4 applicator, positionedproximate the FIG. 3 wafer fragment.

FIG. 12 is a view of the FIG. 3 wafer fragment undergoing processing inaccordance with one embodiment of the invention.

FIG. 13 is a view of the FIG. 3 wafer fragment undergoing processing inaccordance with one embodiment of the invention.

FIG. 14 is a view of portions of an etchant applicator constructed inaccordance with one embodiment of the invention.

FIG. 15 is a view of a wafer fragment undergoing processing inaccordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws "to promote the progressof science and useful arts" (Article 1, Section 8).

Referring to FIGS. 1 and 2, a semiconductor wafer is shown generally at20 and comprises a semiconductive substrate 21. In the context of thisdocument, the term "semiconductive substrate" is defined to mean anyconstruction comprising semiconductive material, including, but notlimited to, bulk semiconductive materials such as a semiconductive wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term "substrate" refers to any supportingstructure, including, but not limited to, the semiconductive substratesdescribed above. Substrate 21 includes a discrete area 22 from whichmaterial is desired to be removed. Discrete area 22 can comprise anyarea from over or within which material is desired to be removed, whilenot subjecting other substrate areas to the removal media or etchantwhich is used. In the preferred embodiment, discrete area 22 comprisesan area containing alignment marks.

Referring to FIG. 2, a layer 24 is formed over substrate 21 andpatterned to define alignment marks 26 which, in this example, areformed over a discrete area of wafer 20.

Referring to FIG. 3, a material has been formed over the wafer and thesurface has been planarized, typically by using a chemical mechanicalplanarization process leaving residue 28 over the substrate and withinalignment marks 26. Residue 28 can comprise any residual material. Inthis example, such material can include chemical mechanicalplanarization process slurry material, a refractory metal, aphotoresist, dielectric material, polysilicon material, e.g., anyresidue from a semiconductor manufacturing process which might bepresent in or over alignment marks 26. In a preferred embodiment,residue 28 comprises an oxide film which is subsequently removed.

Referring to FIG. 4, an etchant applicator in accordance with oneembodiment of the invention is shown generally at 30 and includes a stemportion 32 and a tip portion 34 connected therewith. Stem portion 32 canbe dimensioned to be gripped or held by an individual during use. Stemportion 32 can also be configured for automated use by processingequipment. Liquid etchant material is provided over tip portion 34 whichcan then be used to treat a discrete area on a wafer. Any liquid etchantmaterial can be used, and an exemplary material comprises hydrofluoricacid utilized in concentrations which are normally used during etchingof various materials.

Referring to FIGS. 5-8, four exemplary tip portions are shownrespectively at 34a, 34b, 34c and 34d.

Referring to FIG. 5, tip portion 34a comprises a fluid-permeablematerial 36. As used in the context of this document, the term"fluid-permeable material" is intended to include materials which arecapable of holding or being penetrated with liquid etchant materials.Penetration can occur through openings, pores, interstices, spacesand/or other similar structure in the material. Such materials includethose through which liquid etchant material diffuses, pervades, absorbs,and/or saturates. Accordingly, material 36 can include fibrous materialsuch as a plurality of fibrous members or fibers 38. Exemplary fibrousmembers include Teflon™ or Gortex™ fibers.

Referring to FIG. 6, tip portion 34b comprises a fluid-absorbentmaterial 40. As used in the context of this document, the term"fluid-absorbent material" is intended to include materials which arecapable of taking up or drinking in liquid etchant material.

Referring to FIG. 7, tip portion 34c includes a body 42 having a hollowopening 44 into a cavity in which a portion of a droplet 46 is disposed.A projected portion 48 of droplet 46 projects outward of hollow opening44 and is suspended or clung onto tip portion 34c for purposes whichwill become evident below.

Referring to FIG. 8, tip portion 34d comprises a wick assembly 50 havinga plurality of fibers or fibrous members 52. Wick assembly 50 comprisesmaterial which is configured to receive an amount of liquid etchantthrough wicking action. Accordingly, exemplary materials for wickassembly 50 include fluid-permeable materials and fluid-absorbentmaterials such as those mentioned above.

Referring to FIGS. 9 and 10, an amount of liquid etchant 54 is providedover tip portions 34, 34b respectively. Tip portion 34 can include anyof the above-described tip portions (FIGS. 5-8), and liquid etchant 54can be provided thereover in any suitable way. For example, liquidetchant 54 can be absorbed into, within, onto or through the materialcomprising tip portion 34. In this way, liquid etchant material can beclung onto, supported by, or suspended by the tip portion. In FIG. 10,liquid etchant material is provided over tip portion 34b by dipping orimmersing some or all of the tip portion into an amount of liquidetchant 54. The liquid etchant is absorbed by tip portion 34b. As theliquid etchant is absorbed by tip portion 34b, the illustrated pores(not specifically designated) expand slightly in a sponge-like fashion.

Referring to FIG. 11, the etchant applicator, including tip portion 34(not necessarily shown to scale), is moved into proximity with adiscrete area 22.

Referring to FIGS. 12 and 13, liquid etchant material 54 is transferredfrom tip portion 34 onto discrete area 22. In a first embodiment (FIG.12), tip portion 34 is moved or placed, together with the suspended orclung liquid etchant material, sufficiently close to discrete area 22,e.g. touching the discrete area, to transfer at least some of material54 onto the discrete area. Such constitutes one example of placing thetip portion into proximity with discrete area 22 sufficiently to bringat least some of the etchant material into physical contact withdiscrete area 22. Removing tip portion 34 thereafter leaves at leastsome etchant material 54 behind on the wafer.

Referring to FIG. 13, tip portion 34c is moved sufficiently close todiscrete area 22 to transfer at least some of the suspended or clungliquid etchant material 54 onto discrete area 22. In this example, thetip portion is placed into proximity with the discrete area withoutphysically touching or contacting the discrete area. Removal of the tipportion thereafter results in at least some of the etchant materialbeing left behind on the wafer. Tip portion 34c is used in this examplefor illustrative purposes only. Other above-described tip portions couldbe used in this manner.

Referring to FIG. 14, a liquid etchant applicator assembly in accordancewith another embodiment of the invention is shown generally at 56 andincludes a tip portion 34 and an exhaust outlet 58 proximate tip portion34. Exhaust outlet 58 is configured to remove material from around tipportion 34 during processing. The removed material can include eitherliquid or gaseous material which can be a by-product from the processingtaking place. During treatment of a wafer portion 20 (shown in phantom),exhaust outlet 58 removes material from over the discrete area. Althoughnot specifically shown, exhaust outlet 58 can have inlets through whichmaterial is provided for processing the wafer. In the illustratedexample, the exhaust outlet comprises a vacuum device which isconfigured to remove gaseous material. For example, when processing witha liquid etchant material comprising hydrofluoric acid, fumes can oftenbe generated which are removed through exhaust outlet 58. In theillustrated example, the exhaust outlet comprises a sheath 60 which cantouch the wafer to form a seal therewith during removal of the desiredmaterial. In another embodiment, and one which does not necessarilyrequire an exhaust outlet 58, a reservoir 62 is provided and is in fluidcommunication with tip portion 34. Accordingly, liquid etchant can besupplied to tip portion 34 without resort to dipping the tip portioninto an amount of liquid etchant. Liquid etchant from reservoir 62 canbe provided over tip portion 34 in any suitable fashion. Processing, ofcourse, can take place as described above.

Referring to FIG. 15, etchant applicator 30 can be utilized to treatdiscrete area 22 of wafer 20 by dabbing (arrow A) the area with the tipportion, or by drawing (arrow B) applicator 30 across or through adesired discrete area. The wafer can be dabbed repeatedly with theapplicator. In the case where applicator 30 is used to dab the wafer,and where the liquid etchant material comprises hydrofluoric acid, suchdabbing can take place for no more than about one or two seconds. Longertreatment times can be utilized such as contacting the wafer for oneminute or longer.

Methods and apparatuses of the above-described invention enable liquidetchant material, such as hydrofluoric acid, to be applied over asurface of a wafer with precision and accuracy. Such provides for thedispensing of a small amount of chemical etchant onto a surface to beetched in a highly localized area. Chemicals can be dispensed withlittle or no equipment to regulate flows, such as in conventionalnozzle-like fluid dispensing apparatuses. In addition, the etchantapplicator can be disposable and/or can contain its own fluid reservoir,thereby resulting in considerable equipment savings.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A method of removing material from discrete areason a wafer during processing comprising:suspending a liquid etchantmaterial proximate a tip portion of an etchant applicator; moving theetchant applicator and suspended liquid sufficiently close to a discretearea on a wafer to transfer at least some suspended liquid etchantmaterial onto the discrete area; and retaining the liquid etchantmaterial within the discrete area without using a physical barrier aspart of the etchant applicator.
 2. The method of claim 1, wherein thetip portion comprises a fluid permeable material.
 3. The method of claim1, wherein the tip portion comprises a fluid permeable material having aplurality of fibrous members.
 4. The method of claim 1, wherein the tipportion comprises a fluid permeable material and the suspendingcomprises absorbing liquid etchant onto the material.
 5. The method ofclaim 1, wherein the tip portion comprises a fluid permeable materialand the suspending comprises absorbing liquid etchant through thematerial.
 6. The method of claim 1, wherein the tip portion comprises ahollow opening and the suspending comprises projecting a droplet portionof the liquid etchant material outward of the hollow opening.
 7. Themethod of claim 1, wherein the moving of the etchant applicatorcomprises touching the discrete area with the tip portion.
 8. A methodof removing material from discrete areas on a wafer during processingcomprising:providing an etchant applicator having a tip portion;providing an amount of etchant material over the tip portion, theetchant material being supported by the tip portion; placing the tipportion into proximity with a discrete area of a wafer sufficiently tobring at least some of the supported etchant material into physicalcontact with the discrete area; removing the tip portion from the wafer,at least some of the supported etchant material being left behindthereon; and retaining any liquid portion of the etchant material withinthe discrete area without using a physical barrier as part of theetchant applicator.
 9. The method of claim 8, wherein the tip portioncomprises a fluid-absorbent material.
 10. The method of claim 8,wherein:the tip portion comprises a fluid-absorbent material; theproviding of the amount of etchant material comprises absorbing theamount of etchant material onto the tip portion; and the placing of thetip portion comprises touching the discrete area with at least some ofthe fluid-absorbent material.
 11. The method of claim 8, wherein the tipportion comprises a wick assembly.
 12. The method of claim 8, whereinthe tip portion comprises a wick assembly having a plurality of fibers.13. The method of claim 8, wherein the providing of the amount ofetchant material comprises immersing the tip portion in an amount of theetchant material prior to the placing.
 14. A method of removing materialfrom discrete areas on a wafer during processing comprising:clinging aliquid etchant material onto an applicator tip portion; moving theapplicator tip portion and clung liquid etchant to sufficientlyproximate a discrete area on a wafer to cause removal of clung liquidetchant material from the tip portion and onto the discrete area; andretaining the liquid etchant material within the discrete area withoutusing a physical barrier as part of the applicator tip portion.
 15. Themethod of claim 14, wherein the applicator tip portion comprises ahollow opening and the clinging comprises projecting a droplet portionof the liquid etchant material outward of the hollow opening.
 16. Themethod of claim 14, wherein the applicator tip portion comprises afluid-absorbent material and the clinging comprises absorbing the liquidetchant material onto the fluid-absorbent material.
 17. The method ofclaim 14, wherein the applicator tip portion comprises a fluid-permeablematerial, and the clinging comprises providing the liquid etchantmaterial into the fluid-permeable material.
 18. The method of claim 14,wherein the moving comprises touching the discrete area with theapplicator tip portion.
 19. The method of claim 14, wherein the movingcomprises touching the discrete area only with etchant material and notany of the tip portion.
 20. A method of removing material from discreteareas on a wafer during processing comprising:providing a liquid etchantapplicator having a fluid-permeable tip portion; providing liquidetchant material over the fluid-permeable tip portion; moving thefluid-permeable tip portion into contact with a discrete area of awafer; removing the fluid-permeable tip portion from the wafer, at leastsome of the liquid etchant material being left behind thereon; andretaining the liquid etchant material within the discrete area withoutusing a physical barrier as part of the etchant applicator.
 21. Themethod of claim 20, wherein the providing of the liquid etchant materialover the fluid-permeable tip portion comprises dipping the tip portionin an amount of liquid etchant material.
 22. The method of claim 20,wherein the fluid-permeable tip portion comprises fibrous material. 23.The method of claim 20, wherein the fluid permeable tip portioncomprises a fluid-absorbent material.
 24. The method of claim 20,wherein the fluid permeable tip portion comprises a fluid-absorbentmaterial, and the providing of the liquid etchant material over thefluid-permeable tip portion comprises absorbing liquid etchant materialwithin the tip portion.
 25. A method of removing material from discreteareas on a wafer during processing comprising:providing a liquid etchantapplicator having a wick assembly thereon configured for receiving anamount of liquid etchant; supporting an amount of liquid etchant withsaid wick assembly; transferring at least some of the liquid etchantfrom said wick assembly onto a discrete area on a wafer; and retainingthe liquid etchant within the discrete area without using a physicalbarrier as part of the etchant applicator.
 26. The method of claim 25,wherein the wick assembly comprises a fluid-absorbent material.
 27. Themethod of claim 25, wherein the wick assembly comprises a plurality offibrous members.
 28. The method of claim 25, wherein said supportingcomprises dipping a portion of said wick assembly into liquid etchant.29. The method of claim 25, wherein said transferring comprises touchingsaid discrete area with the wick assembly.
 30. The method of claim 25,wherein said transferring comprises touching said discrete area withliquid etchant supported by the wick assembly.
 31. A method of removingmaterial from discrete areas on a wafer during processingcomprising:providing a liquid etchant applicator assembly comprising afluid-permeable tip portion and an exhaust outlet proximate the tipportion, the exhaust outlet being configured to remove material fromaround the tip portion; providing the fluid-permeable tip portion withliquid etchant material; moving the fluid-permeable tip portion intocontact with a discrete area of a wafer; transferring at least some ofthe liquid etchant material from the fluid-permeable tip portion ontothe wafer; retaining the liquid etchant material within the discretearea without reliance on any part of the etchant applicator as aphysical barrier; and removing material from over the discrete areathrough the exhaust outlet.
 32. The method of claim 31, wherein theexhaust outlet comprises a vacuum device configured to remove gaseousmaterial.
 33. The method of claim 31, wherein the exhaust outletcomprises a sheath and the removing comprises touching the wafer withthe sheath.
 34. The method of claim 31, wherein the fluid-permeable tipportion comprises a plurality of fibrous members.
 35. The method ofclaim 31, wherein the providing of the fluid-permeable tip portion withliquid etchant material comprises providing a reservoir of etchantmaterial in fluid communication with the tip portion.
 36. A method ofremoving material from discrete areas on a wafer during processingcomprising:providing a liquid etchant applicator comprising afluid-absorbent tip portion; providing a liquid etchant reservoir influid communication with the fluid-absorbent tip portion; absorbingliquid etchant from the reservoir onto the fluid-absorbent tip portion;contacting a discrete area on a wafer with the fluid-absorbent tipportion, the contacting transferring some of the liquid etchant onto thediscrete area; and retaining the liquid etchant within the discrete areawithout using a physical barrier as part of the etchant applicator. 37.The method of claim 36, wherein fluid-absorbent tip portion comprises afibrous wick.
 38. The method of claim 36, wherein the liquid etchantcomprises hydrofluoric acid.
 39. A method of removing material fromdiscrete areas on a wafer during processing comprising:providing aliquid etchant applicator having a fluid-permeable tip portion; dippingat least some of the tip portion into an amount of liquid etchantmaterial; transferring at least some liquid etchant from the dipped tipportion onto a discrete area on a wafer; and retaining the liquidetchant material within the discrete area without using a physicalbarrier as part of the etchant applicator.
 40. The method of claim 39,wherein the transferring comprises dabbing the discrete area with thetip portion, the dabbing placing the tip portion into physical contactwith the discrete area for no more than two seconds.
 41. The method ofclaim 39, wherein the transferring comprises dabbing the discrete areawith the tip portion, the dabbing placing the tip portion into physicalcontact with the discrete area for no more than one second.
 42. A methodof removing material from over alignment marks on a wafer duringprocessing comprising:providing a substrate having a plurality ofalignment marks thereover; processing the substrate and depositingmaterial over the alignment marks; providing a liquid etchant applicatorhaving a fluid-permeable tip portion; providing liquid etchant materialover the fluid-permeable tip portion; moving the liquid etchantapplicator into proximity with the alignment marks; transferring atleast some of the liquid etchant material from the fluid-permeable tipportion onto the material over the alignment marks; and retaining theliquid etchant material where transferred without using a physicalbarrier as part of the etchant applicator.
 43. The method of claim 42,wherein the transferring comprises touching the wafer with the tipportion.
 44. The method of claim 42, wherein the fluid-permeable tipportion comprises a plurality of fibers.
 45. The method of claim 42,wherein the fluid-permeable tip portion comprises an absorbent material.46. The method of claim 42, wherein the fluid-permeable tip portioncomprises a wick assembly.
 47. A method of removing material fromdiscrete areas on a wafer during processing comprising:providing aliquid etchant applicator having a fluid-permeable tip portion;providing liquid etchant material over the fluid-permeable tip portion;dabbing a discrete area on a wafer with the tip portion sufficiently totransfer liquid etchant material onto the discrete area; and retainingthe liquid etchant material within the discrete area without using aphysical barrier as part of the etchant applicator.
 48. The method ofclaim 47, wherein the dabbing comprises touching the discrete area withthe tip portion for no longer than about two seconds.
 49. The method ofclaim 47, wherein the dabbing comprises repeatedly touching the discretearea with the tip portion, at least one of the touchings comprisingtouching the discrete area for no longer than about two seconds.
 50. Amethod of removing material from discrete areas on a wafer duringprocessing comprising:providing a liquid etchant applicator having afluid-permeable tip portion; providing liquid etchant material over thefluid-permeable tip portion; touching a discrete area on a wafer withthe tip portion sufficiently to transfer liquid etchant material ontothe discrete area; while the tip portion is touching the wafer, movingthe tip portion across a surface of the wafer; and retaining the liquidetchant material within the discrete area without using a physicalbarrier as part of the etchant applicator.